Identification and characterization of Laodelphax striatellus (Insecta: Hemiptera: Delphacidae) neutral sphingomyelinase.

The neutral sphingomyelinase (nSMase) 1 homologue gene LsSMase was cloned from Laodelphax striatellus, a direct sap-sucker and virus vector of gramineous plants, and expressed via a Bac to Bac baculovirus expression system. The LsSMase-enhanced green fluorescent protein fusion protein was located in the endoplasmic reticulum in a similar manner to mammalian nSMase 1. The biochemical properties of LsSMase were determined in detail. The optimal pH and temperature for recombinant LsSMase were 8 and 37 °C, respectively. LsSMase was an Mg2+ or Mn2+ dependent enzyme, but different concentration of each were needed. The activity of LsSMase was significantly stimulated by Ethylene glycol bis(2-aminoethyl ether)tetraacetic acid (EGTA), whereas it was inhibited by ethylenediaminetetraacetic acid. Millimolar concentrations of Zn2+ completely inhibited LsSMase. The reducing agents dithiothreitol and ß-mercaptoethanol varied in their effects on activity. Phospholipids were not found to stimulate LsSMase.

A Novel Aberrant Splice Site Mutation in RAB23 Leads to an Eight Nucleotide Deletion in the mRNA and Is Responsible for Carpenter Syndrome in a Consanguineous Emirati Family.

Carpenter syndrome is caused by mutations in the RAB23 gene that encodes a small GTPase of the Rab subfamily of proteins. Rab proteins are known to be involved in the regulation of cellular trafficking and signal transduction. Currently, only few mutations in RAB23 have been reported in patients with Carpenter syndrome. In this paper, we report the clinical features, molecular and functional analysis of 2 children from an Emirati consanguineous family with this syndrome. The affected children exhibit the typical features including craniosynostosis, typical facial appearance, polysyndactyly, and obesity. Molecular analysis of the RAB23 gene revealed a homozygous mutation affecting the first nucleotide of the acceptor splice site of exon 5 (c.482-1G>A). This mutation affects the authentic mRNA splicing and activates a cryptic acceptor site within exon 5. Thus, the erroneous splicing results in an eight nucleotide deletion, followed by a frameshift and premature termination codon at position 161 (p.V161fsX3). Due to the loss of the C-terminally prenylatable cysteine residue, the truncated protein will probably fail to associate with the target cellular membranes due to the absence of the necessary lipid modification. The p.V161fsX3 extends the spectrum of RAB23 mutations and points to the crucial role of prenylation in the pathogenesis of Carpenter syndrome within this family.